Oil pressure generated in a mechanical oil pump driven by the engine is supplied to a belt-type continuously variable transmission. Pulley pressures (including a primary pulley pressure and a secondary pulley pressure) generated by using the oil pressure as a source pressure are supplied to a primary pulley and a secondary pulley. These pulley pressures are used to hold a belt and these pulley pressures are controlled to change a groove width in each of the pulleys in order to realize a shift.
JP2005-226802A describes that, in such a continuously variable transmission, in making an idle stop of the engine, it is discontinued to drive a mechanical oil pump and allows no supply of an oil pressure. In order to avoid this situation, there has been known an accumulator for accumulating an oil pressure in order to supply an oil pressure of the accumulator in an idle stop.